General principles • The specious attraction of anecdotes • The concern for precise measurement • Operational definitions – definitions which specify the procedure used to measure something • Also, a way to give a study’s focus of concern a numerical value • How do you measure anger, love, intelligence?
Population samples • Population – the entire group of individuals of interest Sample – a small group chosen from the popu- lation
Types of samples • Convenience – a sample chosen because of its availability • Far from ideal, but very common “The study of 20 year old college sophomores.” ? • Representative – a sample which closely mirrors the population in all characteristics likely to affect the results • Ideal but hard to find
Samples cont. • Random samples – a sample in which every individual in the population has an equal chance of being selected. • Hard to get, but many benefits • Cross-cultural samples – samples which include groups from at least two separate cultures • Discuss concerns in Interpretations
Research designs • Naturalistic observations • A careful examination of an individual’s or animal’s behavior in more or less natural conditions No manipulation, just observation Often the first step in generating hypothesis’
Case histories • A thorough description of a person or small group of people with unusual or noteworthy qualities Another source of hypothesis’ Just a super-sized anecdote?
surveys • A study of the prevalence of certain beliefs, behaviors, or attitudes based upon people’s responses to specific questions • Many problems: sampling nonchalance the questions bias
correlations • A measure of the relationship between two variables • Variable – a measurable item that can vary in magnitude • Correlational study – a procedure in which the investigator measures the relationship between two variables without controlling either one
Correlationsexamples • Between class attendance and final grade • Between hours worked and $ earned • Between smiles given and smiles received • Between miles run/week and 5k time • Between hours on internet and final grade • Between exercise sessions and weight • Between hair color and grade point average
The correlation coefficient • R = the mathematical relationship between two variables, ranging from -1 to 1 • Positive correlations approach 1 • Negative correlations approach -1 • A R of 0 means that there is no relationship between the two variables • Look to R’s absolute value when assessing its strength
Illusory correlations • An apparent relationship based upon casual observations of unrelated or weakly related events • Do people really get wild under a full moon? Does the weather affect arthritis symptoms?
Correlations and causation • No matter how it might seem, correlations do not tell us about cause and effect • We never really know if changes in one variable affects the other, or • If a third, lurking, variable controls them both. • Correlations help us predict but not explain or control behavior or experience.
experiments • A study in which the investigator manipulates at least one variable while measuring at least one other variable • By adjusting one variable or factor, while keeping all other factors constant, we can determine if that factor causes changes in the other(s)
More definitions:variables • Independent variable – the variable which is manipulated, or adjusted, by the investigator • Dependent variable – the variable which is measured by the investigator to determine the effects of the independent variable • Thoughtfully quantified through the operational definition
Even more:groups • Experimental group – receives the treatment (independent variable) that the experiment was designed to test • Control group – handled exactly the same as the experimental group except for the independent variable • Control groups usually receive a placebo
Hazards to be prepared for • Biased groups • to make sure that the experimental and control groups are as similar as possible, before being introduced to the independent variable we use random assignment • every participantmust have anequal chance of being placed in either the experimental or the control group
more hazards • Even unconsciously, investigators want to see their hypothesis confirmed and unintentionally might distort the results • Also, the experiment’s participants might try to help prove the hypothesis Solution – Double blind – a procedure in which both the observer and the participant are unaware of which participants received which treatment and the experiment’s goals
review • Hypothesis • Select Method & Operational Definition • Acquire Sample • Random Assignment of groups • Run experiment (double blind) • Collect and analyze results (data)